I put Maurice Druon's series The Accursed Kings on my reading list several years ago, largely because I saw that George R. R. Martin referenced it as a major influence in his creation of A Song of Ice and Fire. Then I promptly forgot about it, until my recent binge on historical fiction (The Ivy Crown, A Very English Scandal) brought it to mind.
The series takes place mostly during the 14th century in France, from the last of Phillip the Fair's reign until the time of John the Good. The characters are many and varied, from royalty and courtiers to merchants and peasants. There are six books, which sounds long but really went quickly, as each book is fairly short and there's no lack of interesting activity to keep the reader turning the page. (There's a seventh book as well, but it was written many years later and doesn't quite fit with the rest. The library didn't have it, so I stopped at six.) Credit to both Druon and translator Humphrey Hare for well-crafted writing that maintains the reader's interest!
There's no lack of action and intrigue in the series, which I'm sure is part of why Druon chose to wrote about this particular time period. Love affairs, embezzlement, blackmail, secret plots against the powerful, torture and executions, conflict internal to France and externally with England...plenty of material to work with! Much of it centers around Robert of Artois, either directly or indirectly, who is clearly the author's favorite figure from the time. And with good reason, as his actions had huge impact on the direction of both France and England during his life. Robert wasn't a good man, but was certainly a very influential one, and his story is incredibly interesting.
Occasionally the author steps outside the story and speaks directly to the reader about medieval society and events of the time, which I thought added to the feeling of listening to a great storyteller. Unfortunately, this also occasionally spoils some of the suspense for any reader who doesn't already know the fate of the various monarchs and nobles. I think Druon assumes that most of his readers have studied history in enough detail to already know who became king/died/was imprisoned/etc, and so doesn't worry about occasionally talking about future events.
I can definitely see the influence on Martin's work. The various factions playing the "game of thrones" have plenty of similarities to those in The Accursed Kings books. The intrigues and plots of 14th century France would fit right into the world of Westeros and Essos. Inspiration for individual characters can be seen on a regular basis: Enguerrand de Marigny reflected in Eddard Stark, or Marie of Hungary in Olenna Tyrell. Martin added magic and dragons, of course, but even there you see some reflection in Druon's writing when lack of understanding leads people to interpret poison as magic or the suffering of a stroke as the fulfillment of a curse.
For any historical fiction fan, The Accursed Kings series is a must-read. If you're not yet such a fan, read it anyway, you might become one.